Histological study of the effect of COVID 19 on the olfactory mucosa of patients with post COVID-19 olfactory dysfunction

Abstract

Background: Corona viruses affect both humans and birds. In humans, the symptoms vary from mild cough, sore throat to severe respiratory tract infection and respiratory distress. COVID-19 can be presented by cough, difficult breathing, generalized body aches, loss of smell and taste. The sudden loss of smell was described as a definitive diagnostic symptom of COVID-19 infection. This study was designed to investigate the histological changes of COVID19 on olfactory mucosal epithelium, which was associated with temporary or long lasting olfactory dysfunction.

Patients and Methods: This was a prospective study. Twenty patients with olfactory dysfunction few months after COVID 19 were included and represented the study group. In addition, 20  patients with olfactory dysfunction due to causes other than COVID 19 (e.g., allergic nasal polypi or to skull base fracture) were included as the comparison (control group). All were evaluated in a standard techniques. Then, Forty (40) nasal olfactory epithelium punch biopsies have been obtained under general anesthesia after taking a written consent. Data were recorded and compared between both groups.

Results: The Light Microscopic examination of biopsies in the study group showed inflammatory changes among 17 cases and atrophied changes among 3 cases, compared to 16 and 4 cases in the control group. The inflammatory changes were in the form of inflammatory lymphocytic cells, few macrophages, mast and goblet cells. There was no significant differences between groups regarding patient age, special habits, chronic diseases, complications after biopsy or the result of biopsy. However the duration of OD was significantly longer in the patient than the control group (6 (4-8) vs 2 (1-5) months).

Conclusion: COVID 19 invades nasal olfactory epithelium leading to reversible inflammatory changes that was presented as a reversible olfactory dysfunction. These changes did not differ significantly than other causes nasal inflammation.